High redshift submillimeter galaxies

The extragalactic background light (EBL) maps the integrated energy output from stars and active galactic nuclei throughout the universe. In the submillimeter, the EBL has a strength that is comparable to the EBL in the optical. Therefore the submillimeter EBL, the dust-reprocessed emission, shows that much of the cosmic history of star formation and black hole accretion is hidden by dust. The goal of this work is to use the submillimeter EBL sources to understand the cosmic star formation history at high redshifts.;We present an intensive 850 mum survey carried out with the SCUBA instrument on the James Clerk Maxwell Telescope on Mauna Kea. The survey covers an area of ∼110 arcmin2 in the Great Observatories Origins Deep Survey-North (GOODS-N) region with a 0.4-4 mJy sensitivity (1 sigma) and resolves 20--30% of the submillimeter EBL into point sources in the 2--20 mJy flux range. Approximately 60% of the detected submillimeter sources have counterparts in the deep radio image of the GOODS-N. Optical spectroscopic redshifts, photometric redshifts, and millimetric redshifts of the 4 sigma submillimeter sources are in the z ∼ 1.6--3.4 range and the lower limit of their median redshift is at z ∼ 2.4. We break through the 2 mJy sensitivity limit by using the multiwavelength data in the GOODS-N field to conduct stacking analyses in our SCUBA map. We find that galaxies in deep 1.6 and 3.6 pin images resolve ∼ 50 to 70% of the 850 mum EBL. With highly complete redshifts for the 1.6 and 3.6 mum galaxies and their spectral energy distributions, further analyses show that most of the resolved submillimeter EBL arises from galaxies with intermediate spectral types at z = 0--1.5. This redshift distribution of the faint submillimeter sources is significantly lower than that inferred from the bright submillimeter sources and this requires a revised star formation history with a lower star formation rate at high redshifts. We use stacking analyses in the deep radio image to show that the star formation history at z > 1 is relatively flat and that more than half of the star formation occurs at z < 1.4.